A surge protector (or surge suppressor) is a circuit designed to protect electrical devices from damaging electrical overvoltage conditions. A surge protector regulates the power applied to an electric device by either blocking or by shunting currents that are above a safe threshold.
Surge protectors are often used to protect sensitive electronic devices. For example, surge protectors may be provided in A.C. power strips or in rack-mounted power supplies for computer systems. Providing a surge protector in a compact format is relatively rare, however, due to the difficulty of handling large, transient surges with small electrical and/or electronic devices.
In U.S. Pat. No. 4,907,118 a plug-type surge protector is described having a metal oxide varistor which is visible through the plug body. In response to an overload condition, the varistor acts as a one-time fuse to prevent damage to a protected electronic apparatus. The surge protector must then be replaced after it served its purpose.
In U.S. Pat. No. 4,862,311 an overvoltage protector for use with data cables is described which uses a bipolar silicon avalanche diode for surge protection. However, the apparatus of Rust et al. is designed for the relatively low voltages and currents carried by data cables and is not well suited for surge protection of A.C. power lines.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.